Ejectors have been in use for many years, sharing the basic functions of exhausting fluids or evacuating fluid-filled containers. They are known generally as ejectors or jet pumps and operate on the principle of one fluid (a motive fluid) entraining a second fluid. The functions being basically the same, the distinction within the art lies primarily in the design and construction of these ejectors or jet pumps.
All ejectors have three common features: an inlet, a port which allows the induction of the motive or operating medium (fluid) under pressure; suction or quasi-suction, a functional aspect which begins the entrainment process; and discharge, the stage wherein motive fluid energy is imparted to the fluid which is to be exhausted or pumped.
Pressurized pumping medium, hereinafter known as motive fluid, enters the inlet and travels through a nozzle or constricting aperture into the suction chamber. The purpose of the nozzle is to condition the motive fluid, generally by converting the pressure of the motive fluid into a high velocity stream which passes from the exit side of the inlet nozzle immediately to the inlet side of a discharge or ejector tube.
Ejecting or pumping action begins when an entrainment fluid in the suction chamber is captured or entrained by the high velocity stream emerging from the inlet's downstream nozzle. The venturi phenomenon effects lowering of the pressure in the suction chamber. The resulting action causes the entrainment fluid in the suction chamber to flow towards the discharge or ejector tube outlet urged by, and with, the motive fluid.
In the general ejector case, the entrained fluid from the suction chamber mixes with the motive fluid and acquires part of its energy in the downstream, discharge tube section. Normally, a diffuser section is provided adjacent and downstream of the discharge tube. Part of the velocity of the motive-entrained fluid mixture is converted to a pressure greater than the suction pressure, but lower than the motive fluid pressure. It is finally discharged at the diffuser exit port.
The amount of entrainment fluid which can be entrained by the motive fluid is dependent upon the amount of suction produced in the suction chamber from the discharge of the motive fluid through the suction chamber. Limitations on conventional ejector efficiency occur when large quantities of entrained fluid are elicited from a relatively small ejector unit. Because the vacuum produced by Venturi effect in these units is very limited in the amount of entrainment fluid which it may capture, the only reasonable way to increase the entrainment capacity of an ejector is to increase its size. Conventional ejectors possessing a single inlet nozzle and discharge nozzle are thus limited in the range of fluid flow volume that may be expected.
Compounding the disadvantageous low volume capability of most ejectors is their inherent lack of ability to compress the entrained fluid to high pressures. This derives from the fact that entrainment is essentially a boundary layer phenomenon. The motive fluid captures the entrained fluid between its boundary and the walls of the discharge tube. There is generally a mixture of the two fluids as energy is transferred from the motive to the entrained. This phenomenon is dependent upon many factors, not the least of which is solubility of the entrained fluid in the motive fluid or vice versa. In fact, if the two fluids are immiscible, a great deal of the efficiency of the ejector is lost. To act as a high pressure compressor, as most pumps are capable, the ejector or jet pump art obviously depart from the conventional entrainment principles that are employed today.
It is therefore an object of this invention to provide a variable volume ejector which can function relatively free from the limitations of size.
It is also an object of this invention to provide a variable volume ejector which will provide efficient operation over a wide range of fluid flows.
It is another object of this invention to provide an ejector which may be used to pump gaseous fluids as well as liquid fluids.
It is yet another object of this invention to provide an ejector which is capable of entraining a greater quantity of fluid than do conventional ejectors of comparable size.
It is a major object of this invention to make use of a principles of ejection by positive displacement means rather than conventional entrainment.
Finally, it is an object of this invention to provide means by which the aforesaid positive displacement (of entrained fluids) can be achieved; such a method contemplates the urging of entrained fluid by use of the momentum and confinement of hydraulic slugs rather than boundary layer entrainment.
I have described the operation of certain conventional fluid pumps--jet pumps and ejectors--in order to set out the standard of current art. I shall describe my invention hereinafter in terms of specified embodiments which shall be set forth in general form. The objects of the invention, having been set forth in part herein, will be readily seen or may be learned by practice with the invention.